I don't, in fact, speak Japanese as a functional language, or pretend to any deep cultural knowledge of Japan. So sort of your second option; I'd be emitting that noise expecting to trigger the same concept that would be triggered by the common translation "do your best" in an English speaker (with the extra warm glow of anime-fan group affiliation).
And I probably wouldn't do so to an actual native speaker, because of paranoia that I'm not properly modeling their experience, which may not make sense.